javax.servlet
public class UnavailableException extends ServletException
When a servlet or filter is permanently unavailable, something is wrong with it, and it cannot handle requests until some action is taken. For example, a servlet might be configured incorrectly, or a filter's state may be corrupted. The component should log both the error and the corrective action that is needed.
A servlet or filter is temporarily unavailable if it cannot handle requests momentarily due to some system-wide problem. For example, a third-tier server might not be accessible, or there may be insufficient memory or disk storage to handle requests. A system administrator may need to take corrective action.
Servlet containers can safely treat both types of unavailable exceptions in the same way. However, treating temporary unavailability effectively makes the servlet container more robust. Specifically, the servlet container might block requests to the servlet or filter for a period of time suggested by the exception, rather than rejecting them until the servlet container restarts.
Version: $Version$
| Constructor Summary | |
|---|---|
| UnavailableException(Servlet servlet, String msg) | |
| UnavailableException(int seconds, Servlet servlet, String msg) | |
| UnavailableException(String msg)
Constructs a new exception with a descriptive
message indicating that the servlet is permanently
unavailable.
| |
| UnavailableException(String msg, int seconds)
Constructs a new exception with a descriptive message
indicating that the servlet is temporarily unavailable
and giving an estimate of how long it will be unavailable.
| |
| Method Summary | |
|---|---|
| Servlet | getServlet() |
| int | getUnavailableSeconds()
Returns the number of seconds the servlet expects to
be temporarily unavailable.
|
| boolean | isPermanent()
Returns a boolean indicating
whether the servlet is permanently unavailable.
|
Deprecated: As of Java Servlet API 2.2, use UnavailableException instead.
Parameters: servlet the Servlet instance that is
unavailable
msg a String specifying the
descriptive message
Deprecated: As of Java Servlet API 2.2, use UnavailableException instead.
Parameters: seconds an integer specifying the number of seconds
the servlet expects to be unavailable; if
zero or negative, indicates that the servlet
can't make an estimate
servlet the Servlet that is unavailable
msg a String specifying the descriptive
message, which can be written to a log file or
displayed for the user.
Parameters: msg a String specifying the
descriptive message
In some cases, the servlet cannot make an estimate. For
example, the servlet might know that a server it needs is
not running, but not be able to report how long it will take
to be restored to functionality. This can be indicated with
a negative or zero value for the seconds argument.
Parameters: msg a String specifying the
descriptive message, which can be written
to a log file or displayed for the user.
seconds an integer specifying the number of seconds
the servlet expects to be unavailable; if
zero or negative, indicates that the servlet
can't make an estimate
Deprecated: As of Java Servlet API 2.2, with no replacement. Returns the servlet that is reporting its unavailability.
Returns: the Servlet object that is
throwing the UnavailableException
If this method returns a negative number, the servlet is permanently unavailable or cannot provide an estimate of how long it will be unavailable. No effort is made to correct for the time elapsed since the exception was first reported.
Returns: an integer specifying the number of seconds the servlet will be temporarily unavailable, or a negative number if the servlet is permanently unavailable or cannot make an estimate
boolean indicating
whether the servlet is permanently unavailable.
If so, something is wrong with the servlet, and the
system administrator must take some corrective action.
Returns: true if the servlet is
permanently unavailable; false
if the servlet is available or temporarily
unavailable